1. Field of the Invention
This invention relates to bulk liquid storage tanks, and in particular to an improved tank gauge for measuring the amount of liquid within the tank and for monitoring the movement or settling of the storage tank.
2. Background of the Invention
Bulk fuel storage tanks can range from about 2,500 gallons up to about 1,000,000 gallons in capacity. Above-ground storage tanks (ASTs) are regulated by various federal and state authorities who distinguish between storage tanks and dispensing tanks.
In bulk storage tanks, especially bulk fuel storage tanks, it is necessary to be able to quickly and safely measure the amount of fuel within the tank. Some products have consisted of an internal float or other measuring mechanism which is connected to either a mechanical or electrical readout for providing information on the amount of liquid within the tank.
For instance, U.S. Pat. No. 37,709 to Smedley discloses an oil still for drawing water off and separating it from oil.
U.S. Pat. No. 532,868 to Bull discloses an electrical annunciator having a float for water tanks that sets off an alarm when a certain capacity is reached or the tank becomes empty, and discloses a trolley connected on a cable strung between the float and the counterpoise.
U.S. Pat. No. 872,753 to Runyun discloses an indicating and registering device for railroad water tanks and reservoirs having a float attached to a rope and pulley, and a counter-weight, the counter-weight having a series of wheels with teeth and trip pins for registering the distance travelled.
U.S. Pat. No. 5,425,329 to Pollock discloses a feed bin fill indicator having a flag that moves vertically along an external track having a reference position.
U.S. Pat. No. 5,050,432 to Barritt discloses a tank gauge for oil tanks having a double pulley on a common shaft which is journaled in the wall of a sealed housing, one of the pulleys attached to a 13 pound float on the interior of the tank, the other pulley attached to a 9 pound weight on the exterior of the tank.
U.S. Pat. No. 7,129,832 to Sabatino discloses a high/low level alarm controller having the ability to interface with level sensing equipment.
U.S. Pat. No. 4,459,584 to Clarkson discloses an automatic liquid level indicator and alarm system for petroleum storage tanks, having an intra-tank float with magnets that moves vertically between magnetic sensors connected to an RF transmitter.
U.S. Pat. No. 4,709,653 to Salomon discloses a mechanical fluid indicator on a continuous loop belt having a float and marking elements affixed thereon.
U.S. Pat. No. 4,890,493 to Johnson et al. discloses an automatic tank reading gauge in the shape of a vertical loop having a clear sight area at the top for viewing marking related to the amount of fluid, and which protrudes from the tank being measured.
U.S. design Pat. D334,718 to Basden et al. discloses a liquid storage tank gauge in the form of a cylinder having indicia marked thereon.
U.S. Pat. No. 2,949,777 to Ferron discloses a liquid level gauge for measuring liquid levels of tall tanks, and includes a mirror for observing the volume reading, the mirror being mounted on a gauge system having pulleys and counterweights and an intra-tank float.
However, in systems where the gauge includes a cylindrical tube having a marker disposed within the tube, the cylindrical tube is made from plastic, and although this product appears to solve the problem of determining remaining capacity, unexpected problems have arisen.
One problem stems from the fact that the cylindrical tube was made from plastic in order to save expense and make manufacturing easier. However, it has been determined that the capacity markings, or indicia, on the side of the plastic cylinder often wear off after being subjected to environmental conditions over time.
Other commercial embodiments, are attached to the steel aboveground fuel storage tank using a fiberglass mount, which also gets subjected to environmental wear and tear over time